This invention relates generally to antennas, and in particular to a retractable antenna for electronic devices.
An antenna is a lossy transducer that transforms energy from one form to another. Antennas are employed to transmit or receive radio frequency (RF) electromagnetic radiation. The same antenna may be used to both transmit and receive RF energy. As a transmit antenna, an antenna receives electrical energy from a source, such as a feed line coupled to the antenna, and radiates the received electrical energy less some loss into the space surrounding the antenna. As a receive antenna, the antenna converts electrical energy from the space surrounding the antenna into electrical energy and couples the induced electrical energy to a feed line coupled to the antenna. Electronic devices, particularly portable devices such as portable or cellular telephones, two-way radios, and personal digital assistants, interface with each other through, inter alia, RF communications using such standards as IEEE 802.11, Bluetooth, and others.
Electronic devices generate RF noise that may be coupled to an antenna thereon. Cell phones and radios have employed sliding or telescoping antennas to extend the antenna to an appropriate length or provide for greater signal reception. Such extending antennas do not reduce noise pick-up.
It would be desirable to have an antenna on an electronic device that can be positioned so as not to be electromagnetically coupled to noise generating sources of the electronic device.
In accordance with an illustrative embodiment of the invention, an electronic device includes a retractable antenna. The antenna is spring loaded and when in use extends beyond the profile of the housing of the electronic device. The antenna is retracted to within the profile of the housing of the electronic device when not in use. Preferably the antenna is spring loaded to move from the retracted position to the extended position upon actuation. In one embodiment, the antenna is a quadrifilar antenna. The antenna may be incorporated in an on-off switch.